A conventional air-conditioning system that has an emergency power supply to supply electric power during an emergency (such as a commercial power supply failure), and that is configured to be operated by a commercial power supply during normal operation has been known. The air-conditioning system includes one or both of a battery and a private power generator (Patent Literature 1, for example) as an emergency power supply.
In the air-conditioning system of Patent Literature 1, when the feeding state is switched to a state where power is fed from an emergency power supply due to power failure or other factor, the emergency power supply transmits a power feeding signal to a controller. In response, the controller that received the power feeding signal from the emergency power supply sets the compressor to its lowest frequency and sets the fan to its lowest air flow rate.